Unidirectional Pinning and Hysteresis of Spatially Discordant Alternans in Cardiac Tissue

TL;DR

This paper investigates the dynamics of spatially discordant alternans in cardiac tissue, revealing a novel unidirectional pinning mechanism of nodal lines that influences arrhythmogenic behavior.

Contribution

It introduces a new nonlinear bifurcation mechanism causing unidirectional pinning of nodal lines in calcium-driven alternans, advancing understanding of arrhythmia precursors.

Findings

Discontinuous calcium alternans amplitude at nodal lines

Unidirectional pinning of nodal lines by bifurcation

History-dependent nodal line motion influences arrhythmia risk

Abstract

Spatially discordant alternans is a widely observed pattern of voltage and calcium signals in cardiac tissue that can precipitate lethal cardiac arrhythmia. Using spatially coupled iterative maps of the beat-to-beat dynamics, we explore this pattern's dynamics in the regime of a calcium-dominated period-doubling instability at the single cell level. We find a novel nonlinear bifurcation associated with the formation of a discontinuous jump in the amplitude of calcium alternans at nodal lines separating discordant regions. We show that this jump unidirectionally pins nodal lines by preventing their motion away from the pacing site following a pacing rate decrease, but permitting motion towards this site following a rate increase. This unidirectional pinning leads to strongly history-dependent nodal line motion that is strongly arrhythmogenic.